This invention relates electronically commutated d-c motor in general and more particularly to an improved control signal generator for the commutating device of such a motor.
A control signal transmitter for the commutating device of an electronically commutated d-c motor, comprising at least two rotor position transmitters, especially magnetic field sensitive components which deliver output signals which depend on the position of the rotor and continuously change in time when the rotor is turned steadily, and an evaluation circuit which derives control signals for the commutating device from the output signals of the rotor position transmitters, the control signals determining the individual switching instants for the switching elements of the commutating device is described in "VDE-Fachberichte", No. 25, 1968, pages 147 to 151, particularly FIGS. 5 and 7. This control signal transmiter is used in connection with an electronic motor, the stator winding of which consists of four individual windings which are located in pairs in winding chambers of a winding body and are arranged spatially and electrically at right angles to each other. The stator winding surrounds a 2 pole rotor magnet. Two magnetic field sensitive components are provided as rotor position transmitters to indicate the position of the rotor magnet, and, more speicifcally, comprise two Hall effect generators which are arranged in a stationary manner and shifted 90.degree. el relative to each other. Each Hall effect generator is arranged on the magnetic axis of an individual winding. This is called "zero-degree shift". The two Hall effect generators are acted upon by the magnetic field of the rotating rotor in such a way that the Hall voltage of one changes sinusoidally with the angle of rotation and that of the other as a cosine function. An evaluation circuit (l.c., FIG. 9) derives control signals for the commutating device from the Hall signal of the two Hall effect generators. This derivation is made from the four intersections of the Hall signals. The commutating device is equipped with four power transistors acting as switching elements, which are connected in series to the individual windings. The currents in the individual windings are controlled by the power transistors. In particular, this may involve 4 pulse operation, in which the evaluation circuit is designed as a so-called 90.degree. circuit. There, the currents of the individual legs follow each other at a spacing of 90.degree. el; practically no overlap takes place.
In the just mentioned literature reference VDE--Fachberichte, No. 25, 1968, an electronic motor with a field plate (magnetic resistance) control is also shown in FIG. 11. This involves a 3 pulse motor, the stator winding of which has three individual windings. The individual legs are shifted 120.degree. el and in space relative to each other. Three field plates, shifted 120.degree. el and spatially relative to each other, are utilized in driving the motor.
A control signal transmitter of the type mentioned at the outset is also known from "Siemens Zeitschrift", April 1971, pages 206 to 208, especially FIG. 2. Here, too, a rotor with one pair of poles is used. The stator winding likewise has four individual windings.
Also, in the disclosed device, two Hall generators shifted 90.degree. el relative to each other are used as rotor position transmitters. However, these are now arranged not axially to the individual windings but at an angle of 45.degree. between the individual windings of the stator winding. This is called "45.degree. shift". The control signals for the commutating device are derived in this case by the evaluation circuit not from the intersections but from the zero crossings of the two Hall voltages. During one rotor revolution commutation takes place four times also in this case; it therefore again involves 4 pulse operation.
From the discussion above it will become clear that, within the state of the art, a stator winding of three individual windings, three rotor position transmitters and a 3-pole operation has been used heretofore, or a stator winding with two rotor position transmitters and 4 pulse operation. 4-pulse operation is also known in an electronic motor having two individual windings through which current flows in both directions. However, in the interest of lower torque ripple and thereby quieter running of the electronic motor, it is desirable in many applications to work with higher pulse operation.